2.1 Field of the Invention
This invention relates to the field of transportation of bulk product. More particularly the invention relates to optimizing scheduling of transportation vessels of bulk products.
2.2 Description of Related Art
Transportation costs of bulk products often represent a substantial portion of the overall cost for said products. Virtually every bulk product, such as, for example, bulk chemicals (e.g., ammonia) and farm products (e.g., grain), is transported and has associated transportation costs that could be optimized. For example, costs for transportation of refinery feedstocks, which include crude oil, as well as gas oils, naphthas, gasoline blending components and other intermediate streams, as well as finished products such as gasoline, could be optimized.
Current approaches to optimizing transportation costs provide only routing scheduling where there is a known cargo, whether it is discrete or bulk product. No current approach considers simultaneously scheduling transportation and managing inventories with non-constant rates of supply (production) and demand (consumption) of the product with a heterogeneous fleet of vessels that may make multiple loads and discharges. In addition, no other known approach uses realistic economic calculations for shipping that include flat rates, demurrage costs and overage calculations.
For example, the shipping of ammonia has been addressed by Christiansen et. al. M. Christiansen, Decomposition of a combined inventory and time constrained ship routing problem, Transportation Science, 33(1): 3-16 (1999). This article poses the problem where inventory management and routing are constrained by time-window requirements and ships are permitted to carry partial loads. A fleet of ships transport a single bulk product between production and consumption harbors. The suggested algorithmic approach breaks the larger problem into sub-problems, which are then solved via dynamic programming as discussed in M. Christiansen and B. Nygreen, Modeling path flows for a combined ship routing and inventory management problem, Annals of Operations Research, 82: 391-412 (1998). Some preprocessing steps are introduced to decrease the problem's complexity in order to speed up run times in M. Christiansen and B. Nygreen, A method for solving ship routing problems with inventory constraints, Annals of Operations Research, 81: 357-378 (1998). The economic calculations of this approach oversimplify real problems and assume constant rates of production and consumption.
The minimum cost inventory routing problem for multiple bulk liquid products (which cannot be mixed) is addressed by D. Ronen, Marine inventory routing: shipments planning, Journal of the Operational Research Society, 53: 108-114 (2002). The ships in this routing problem have multiple compartments and each ship is restricted to loading and unloading at only one port. Additionally, this routing problem only allows a homogeneous pool of vessels.
One commercially available tool for simulating and scheduling shipping is TurboRouter®. This tool, however, does not account for inventory management. Furthermore, the tool is limited in that the pool of vessels must be homogeneous and the vessels can make only one load and one discharge.
There are no existing commercial software tools that jointly route and schedule ships while maintaining inventory profiles. Current practice involves using spreadsheets to manually assign ships to routes and to select load volumes.
A tool or system for optimizing transportation scheduling and inventory management of a bulk product from a group of supply locations to a group of demand locations is needed. There is also a need for a tool or system that facilitates, not only ship selection and routing, but also load/discharge schedules and volumes. Finally, there is a need for a tool or system that provides the optimized results in a practical time frame so that the results may be implemented in a dynamic transportation environment.